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A new study that examines why birds often collide with large structures that are clearly visible to humans — such as buildings, power lines, and wind turbines — suggests it comes down to a fundamental difference in the way birds view the world. While many believe bird flight is controlled primarily by vision, researchers at Birmingham University in England say there is a more subtle combination of relationships between birds’ visual capabilities, interpretation of sensory information, and behavior. “When in flight, birds may turn their heads to look down, either with the binocular field or with the lateral part of an eye’s visual field,” says Graham Martin, a professor of avian sensory science at Birmingham and author of the study
published in The International Journal of Avian Science. “Such behavior results in certain species being at least temporarily blind in the direction of travel.” Avian front vision is also tuned to detect movement rather than spatial details (which is helpful when hunting), and many birds are unable fly slowly, making it difficult to adjust their behavior when visibility is poor. While steps can be taken to reduce bird collisions, the study suggests this can be done only on a species-by-species basis.